What are the causes of persistent hyperkalemia?

Causes of Persistent Hyperkalemia

Persistent hyperkalemia results from three fundamental mechanisms—decreased renal potassium excretion (the dominant cause), transcellular potassium shift out of cells, or excessive potassium intake—with impaired renal excretion being the primary driver in sustained cases. 1

Decreased Renal Potassium Excretion (Primary Mechanism)

Impaired renal excretion is the dominant cause of sustained hyperkalemia because the kidneys are the primary regulators of potassium homeostasis. 1, 2

Chronic Kidney Disease

• The incidence of hyperkalemia increases dramatically with severity of renal impairment, occurring in up to 73% of patients with advanced CKD. 1
• Hyperkalemia risk rises markedly when eGFR falls below 15 mL/min/1.73 m², reflecting severe impairment of renal potassium clearance. 1
• In patients receiving RAAS inhibitors, hyperkalemia risk is already elevated when eGFR < 60 mL/min/1.73 m² and increases progressively as renal function declines further. 1

Acute Kidney Injury

• Acute kidney injury is often accompanied by acute pancreatitis or hepatic failure, and was present in all cases of hyperkalemia-induced cardiac arrest in one retrospective analysis. 1

Hypoaldosteronism

• Hyporeninemic hypoaldosteronism can cause hyperkalemia even in patients with normal or mildly impaired kidney function, particularly in diabetes mellitus. 1, 3
• Heparin and its derivatives suppress aldosterone synthesis, contributing to hyperkalemia. 1

Drug-Induced Hyperkalemia (Most Important Iatrogenic Cause)

Medications, particularly RAAS inhibitors, represent the most important iatrogenic cause of hyperkalemia in everyday clinical practice, with up to 40% of heart failure patients and 5-10% of combination therapy patients developing hyperkalemia. 1

RAAS Inhibitors

• Angiotensin-converting-enzyme inhibitors, angiotensin-receptor blockers, and mineralocorticoid-receptor antagonists lower aldosterone activity, thereby reducing renal potassium excretion. 1
• Among NYHA Class II–IV heart-failure patients who start an MRA, up to one-third develop hyperkalemia (serum potassium > 5.0 mmol/L) within two years of therapy. 1
• In routine clinical practice, hyperkalemia occurs in as many as 50% of patients receiving any RAAS-inhibitor therapy, reflecting a high real-world burden. 1

Other Medications

• Potassium-sparing diuretics (spironolactone, triamterene, amiloride) directly impair renal potassium excretion. 1
• NSAIDs impair renal potassium excretion by reducing prostaglandin synthesis. 1
• Trimethoprim and pentamidine block epithelial sodium channels in the collecting duct, leading to hyperkalemia. 1
• Beta-blockers impair cellular potassium uptake and diminish renin release, increasing the risk of hyperkalemia. 1
• Calcineurin inhibitors (cyclosporine, tacrolimus) impair renal potassium excretion. 1

Transcellular Potassium Shift

Metabolic Acidosis

• Metabolic acidosis causes potassium to shift out of cells in exchange for hydrogen ions. 1

Insulin Deficiency

• Insulin deficiency hampers Na⁺/K⁺-ATPase-mediated cellular potassium uptake, causing a transient rise in extracellular potassium concentration. 1
• Diabetes mellitus increases the risk of hyperkalemia through hyporeninemic hypoaldosteronism and insulin deficiency, even in patients with normal kidney function. 1

Massive Tissue Breakdown

• Rhabdomyolysis, tumor lysis syndrome, and severe burns release large amounts of intracellular potassium. 1

Excessive Potassium Intake

Excessive intake can cause hyperkalemia but usually only in the setting of impaired renal function. 2

• Potassium supplements are a direct exogenous source. 1
• Salt substitutes often contain potassium chloride (e.g., DASH diet products). 1
• High-potassium foods such as bananas, melons, orange juice, potatoes, and tomatoes can contribute to hyperkalemia. 1

High-Risk Comorbidities

Certain patient populations have dramatically elevated risk of developing persistent hyperkalemia. 1

• Advanced CKD, heart failure, diabetes mellitus, resistant hypertension, myocardial infarction, and advanced age are all strongly associated with hyperkalemia. 1
• Advanced age is associated with altered potassium homeostasis, increasing the risk of hyperkalemia even in patients with normal kidney function. 1
• Men have slightly higher risk than women after RAAS inhibitor initiation. 1

Pseudohyperkalemia (Critical to Exclude)

Pseudohyperkalemia represents falsely elevated potassium in the test tube without true elevation in the body and must be ruled out before treating persistent hyperkalemia. 1

• Causes include hemolysis during blood draw, prolonged tourniquet application, fist clenching during phlebotomy, thrombocytosis, or leukocytosis. 1
• If pseudohyperkalemia is suspected, repeat measurement with proper blood sampling technique or obtain an arterial sample for confirmation. 1
• Plasma potassium concentrations are usually 0.1-0.4 mEq/L lower than serum levels due to platelet potassium release during coagulation. 1

Multiple Mechanisms Often Coexist

Multiple mechanisms of hyperkalemia often coexist, such as CKD + RAAS inhibitor + NSAID, making persistent hyperkalemia particularly difficult to manage. 1

• Patients who have both cardiovascular disease and chronic kidney disease experience frequent hyperkalemia episodes, with 50% suffering two or more recurrences within a single year. 1
• Both the absolute potassium level and the rate of rise determine clinical significance, with rapid increases more likely to cause cardiac abnormalities than gradual elevations over months. 1